1. Field of the Invention
The invention concerns the field of conveying and packaging technology and relates to an apparatus for processing continuously conveyed flat products, in particular printed products, and/or a continuously moving, quasi endless material web, in particular a sheet-material web.
2. Description of Related Art
Processing products in a conveying stream requires, on the one hand, high processing speeds and a straightforward, low-wear design for the mechanical components which means that the latter are not particularly susceptible to malfunctioning and, on the other hand, precise control of the movement of the tools and of the products and a processing time which is as long as possible. Most processes used for processing products or a material web, e.g. welding, cutting or printing, also require a certain counterpressure or resistance to be applied by a counterpart tool which interacts with the actual tool. Some of these requirements are met in different ways.
Movement of the tools along a circular path is mechanically straightforward to achieve and is usually preferred. Such apparatuses with welding tools which are moved along circular paths by virtue of a rigid body being rotated are known, for example, from EP-A 1 362 790, WO 00/35757 or WO-A 2005/118402. While the tools in EP-A 1 362 790 or WO-A 2005/118402 are always oriented in the radial direction, the orientation of the tools in WO 00/35757 is kept constant in that the tools are fastened in a rotatable manner on the rotary body and, as the latter rotates, circulate synchronously in the opposite direction.
In the case of the apparatus according to WO 00/35757, the position of the processing zone of the tool, that is to say of that part which interacts with the product or the material web, depends greatly, on account of the distance from the pivot axis, on the quality of synchronization of the counterrotation of the tool with the rotary movement of the rotary body. If guide tracks are used for this purpose, these guide tracks have to be formed very precisely.
The apparatuses according to EP-A 1 362 790 and WO 00/35757 comprise counterpart tools which move synchronously with the actual tool and likewise circulate on a circular path. In order to extend the processing duration, and thus the processing region, the movement paths of the tool and counterpart tool, these paths being circular in the non-loaded state, intersect. Since the tools are mounted resiliently relative to the rotary body, the circulatory path of the tool is flattened by the counterpressure applied by the other tool respectively and the processing region is thus extended. The forces which act on the tools here, however, may lead to wear.
International patent application PCT/CH2007/000130, which was not published before the priority date, proposes, as an alternative to the purely circular path, to connect the tool to the carrying arm in a pivotable manner via a lever arm such that the processing zone is at a distance from the pivot axis and thus, depending on the pivoting position, is at a variable distance from the center of rotation. The pivoting position is adjusted by a control element which interacts with a control track and is located in the region of the processing zone and, thus, likewise at a distance from the pivot axis. In this way, it is possible to produce a circulatory path for the processing zone which differs from a purely circular path, and in particular has a rectilinear segment for extending the processing region. A second control element and a second control track also make it possible to adjust the orientation in space. In the case of this apparatus, the precise position of the processing zone and the orientation and speed thereof during passage through the processing region depend greatly on the accuracy of the control track. The control track, thus, has to predetermine the movement path of the control elements within relatively narrow limits, e.g. if the orientation is to be kept constant. This may give rise to problems when, for example, products of different thicknesses are processed. Moreover, the forces which prevail during processing have to be absorbed via the control elements and control tracks. Undesired torques arise here.
An apparatus for welding a material web without a circulating counterpart tool is known from WO-A 2005/118402. The apparatus comprises a plurality of welding tools which are arranged on a wheel, are always oriented in a radial direction and thus, once again, describe a circular path. Located beneath the wheel is a conveying belt by means of which a material web and also products which are to be wrapped by the material web are conveyed into the processing region of the welding tools. The conveying belt acts as a counterpart tool and itself applies the resistance which is necessary for processing. Although each individual point on the conveying belt is moving, the conveying belt as a whole does not change its position relative to the welding tool, and this does away with any synchronization problems.
In the case of the welding apparatus according to WO-A 2005/118402, the purely circular circulatory path of the tools and of the processing zones thereof, in this case the hot welding zone (welding bars) of welding tools, is arranged such that it undercuts the conveying plane defined by the top side of the non-loaded conveying belt. For this purpose, the conveying belt, which is guided around two stationary rollers, is multilayered and can be compressed perpendicularly to the belt plane. Directed toward the tool is a firm, friction-reducing carrying layer which is a good thermal insulator and is, for example, Teflon-coated, and this is followed by a damping layer, e.g. made of compressible foam, and a base material. The carrying layer is, thus, deflected downward to a slight extent by the pressure of the tool, and the damping layer is compressed. This damping layer can compensate for small undercuts of the conveying plane by the tools in the order of magnitude of a few millimeters. It is not possible, however, to control the orientation of the welding tools in the case of the apparatus according to WO-A 2005/118402.
It is, thus, an object of the invention to reduce the abovedescribed problems of the prior art and to ensure, in particular, precise controllable positioning of the processing zone of the tools in the processing region.
The apparatus according to the invention serves for processing flat articles, in particular printed products, conveyed one after the other in a conveying direction and/or for processing a continuously conveyed material web. A preferred use is that of welding a sheet-material web for packaging products. Other uses are possible, e.g. printing, cutting, application of adhesive, supplying supplementary products.
The apparatus comprises at least one rigid body, which can be rotated about an axis of rotation, e.g. a wheel or a carrying arm, and at least one tool, which is fastened on this body, can be moved along a circulatory path by virtue of the body being rotated and has a processing zone. This tool is, in particular, a welding tool with a welding bar as the processing zone. The tool is fastened on the body such that it can be rotated or pivoted about a pivot axis, wherein the pivoting position of the tool can be adjusted, in dependence on the rotary position of the rigid body, by means of a fixed-location control track (control cam) and a control element which interacts with the control track and is connected to the tool. According to the invention, the pivot axis is at a constant distance from the axis of rotation, and the processing zone of the tool is arranged in the immediate vicinity of the pivot axis, wherein the control element is spaced apart from the processing zone. This design has the advantage that the position of the processing zone in space is known precisely at any point in time because the processing zone is always located on a circular path of which the radius corresponds to the distance of the pivot axis from the center of rotation.
However, the orientation of the processing zone can be adjusted precisely with the aid of the control element and of the control track. Since the control element is spaced apart from the pivot axis, a change in its position does not result in any change, or in only a very slight change, in orientation of the processing zone without a simultaneous change in position relative to the product which is to be processed. In order to achieve a desired level of accuracy, less outlay is thus required for the purposes of configuring and positioning the control track than has been the case hitherto.
Since the processing zone is mounted directly on the rigid body, e.g. on the carrying arm, rather than on a circumferentially projecting lever arm, the force which can be applied during processing is led off in the radial direction. The force is, thus, absorbed directly by the rigid body via the center of rotation thereof. There is no torque arising which has to be absorbed and compensated for. This likewise contributes to an increase in the processing quality and to the stability of the apparatus.
The control track is preferably designed such that the orientation of the tool in space is essentially constant at least in a sub-region of the circulatory path, in particular in, and upstream and downstream of, the processing region. This has advantages, in particular, for welding since the welding bar can be inserted between two products, and come into contact with the material web, vertically.
The apparatus can be used with a moving counterpart tool which is fitted, for example, on a complementary counterpart apparatus. This is advantageous, in particular, in cutting tools which require a counterpart blade.
In a preferred development of the invention, however, the counterpressure which is necessary for processing is applied by the conveying belt of a conveying arrangement without any separate counterpart tool being present. The conveying belt, for this purpose, has mechanical properties adapted to the processing, e.g. strength, heat resistance, low friction.
For this purpose, the apparatus comprises a conveying arrangement for conveying the articles or material web. The conveying arrangement has at least one carrier belt, which is driven in circulation, and deflecting means for deflecting the same. A conveying support for the products or the material web is formed by an outer surface of the carrier belt, this outer surface being directed toward the at least one tool. This conveying support interacts in the processing region, as a counterpart tool, directly or indirectly, i.e. via the product or the material web, with the tool in that it sets against the tool a certain resistance or processing pressure which is necessary for processing purposes.
The advantage of such an apparatus is that only a small amount of space is required and there is no need for synchronization with a counterpart tool. Moreover, the product is fully supported by the carrier belt at any point in time. This allows precise conveying and processing even at high processing speeds.
A hitherto unsolved problem in respect of a counterpart tool which is fixed in location overall, e.g. a conveying belt, is constituted by relatively large degrees of deflection of the conveying belt caused directly or indirectly by the tools, e.g. when the latter, on account of inaccurate supply, strike against a product rather than coming between the products. In the case of a stiff conveying belt, this may result in the tools jamming or being damaged. An elastic conveying belt can compensate for this in some cases, but does not appear, in normal circumstances, to meet the requirements relating to precise feeding of the products (no sagging).
For the purpose of solving this problem, in an advantageous development of the invention, at least one of the deflecting means for the carrier belt is mounted resiliently. Depending on how the resilient mounting is configured, the following advantages may be achieved: if those deflecting means between which the conveying support is defined are resilient, they can change their position in space and, thus, move out of the way of the tool, e.g. when the latter applies pressure to a product instead of alongside the same. If the deflecting means which define the conveying support are fixed, but a further deflecting means is resilient, the resilient mounting can compensate for deflection of the carrier belt. In both cases, the carrier belt itself may thus be comparatively stiff and firm. This makes it possible, using straightforward means, to realize a conveying support which, even under loading, is well-defined, largely planar and does not sag. The further deflecting means prestresses the carrier belt preferably in the outward direction in order, despite the stiffness of the carrier belt, to achieve a planar, non-sagging conveying support.
In a development of the invention, the conveying function of the conveying arrangement is separate from the supporting function by virtue of an additional supporting means being arranged beneath the conveying support, at least in the processing region. This supporting means has a supporting surface which runs parallel to the outer surface of the carrier belt, is directly adjacent to the inner surface of the carrier belt and stabilizes the carrier belt. A largely planar conveying surface is, thus, provided irrespective of the elastic properties of the carrier belt. The carrier belt itself may thus, if appropriate, also be elastic.
As an alternative, or in addition, it is particularly preferred if the supporting means is mounted resiliently, preferably that the supporting surface can be tilted in, and transversely to, the conveying direction. The supporting surface is preferably prestressed in the outward direction toward the carrier belt. The resilient mounting is configured such that the supporting surface remains planar even when tilted. As a result, the conveying support can move out of the way of any disruption, but remains planar in the process.
For the purpose of extending the processing region in the, in this case, circular circulatory path of the processing zone, it is advantageous that the circulatory path of the tool undercuts the conveying plane and the carrier belt or the supporting means has a compressible damping layer for absorbing the deflection of the carrier belt, of usually 10-15 millimeters, which occurs during normal processing.
In particular, when a damping layer is present, the resilient mounting of the conveying support and/or of the supporting means serves, in particular, to compensate for disruption which results in the conveying support being deflected to an extent which is greater than that customary for normal processing.
The apparatus according to the invention is preferably used for welding a material web, e.g. within a sheet-wrapping production line. The tools are welding tools with a welding bar as the processing zone. The carrier belt of a conveying arrangement in the form of a belt conveyor acts as the counterpart tool. Products positioned on a sheet-material web are wrapped by the sheet-material web, and the resulting sheet-material enclosure is then welded transversely to the conveying direction by the welding tools and severed by material displacement during welding, this resulting in two spaced-apart weld seams being formed. Such a processing apparatus will be explained in more detail hereinbelow with reference to the figures.
The products are preferably supplied to the abovementioned conveying arrangement by a belt conveyor. There are advantages if the conveying plane of the conveying arrangement is positioned obliquely, and runs upward, relative to the conveying plane of the belt conveyor. This is explained in more detail hereinbelow with reference to the drawings.
The presence of a removal arrangement, which is arranged downstream of the actual processing apparatus, as seen in the conveying direction, is also preferred. This removal arrangement can preferably grip the processed products or the processed material web, e.g. can fix the same on its conveying belt by means of suction air. It conveys preferably at a greater conveying speed than the abovementioned conveying arrangement. Since the welding zone can also be deformed plastically immediately following processing, it is possible for the sheet-wrapped products, if not severed optimally, to be severed from one another in this way simply by being pulled apart.